2002 S80 2.9 non-turbo brake issue.

Son was driving it and complained of hiss under dash. I noted the vacuum pump motor could be heard intermittently after engine shut down- every time. Obvious vacuum leak, and due to odd hiss under dash, we decided to change the booster. Followed the instructions at the beginning of this thread and it worked out well with a couple of exceptions.

Before I go further, I need to give a shout out to Auto Zone where I purchased a remanufactured booster online. I had a coupon for 20% off of online purchase, and somehow I convinced myself this car had DTSC. Honestly, there is scant info on identifying the difference between DTSC and STC. Looking at my booster (still in the car) and the photos on IPD website-

Volvo Brake Booster - 1999-2009 P2 S60 80 V70 XC70 with DSTC 113495 31273684, 30793677, 8624547, 8649492, 9169200 30793677, 31273684

I was sure mine was DTSC, even though the switch on the lower center dash said "STC". Well, we got the old part out and discovered we only had STC. I figured the DTSC would work, it just has an extra set of sensors and a plug that would be unused, but I paid around ($300 with the discount) and knew the STC unit to be less expensive. Turns out my local AutoZone has the STC unit in stock, and I was able to do an exchange, getting a full refund on the mail order unit. The reman STC unit was $159- lifetime warranty- which seems most reasonable. Thanks AutoZone!

Now as for the exceptions to the instructions- really it was more of a "misunderstanding" on my part when it came to moving the ABS unit. It has three large head screws that hold it to the bracket with large rubber washer insulators in between to avoid noise from the unit transmitting to the cabin. I took these three out. Still, I was not able to maneuver the ABS and attached master cylinder enough to get the booster out. Turns out there are three screws that mount the ABS bracket to the frame, and these needed to be removed- with the bracket- to give enough space to get the booster out. However, I am not sure I could have gotten those three out without removing the first three anyway. There was not room for my hand otherwise.

Also, the position sensor has to be removed from your old unit and placed in the reman unit. There is a silver ring clip that holds this in place. It was not on the reman unit and I had to go rescue it from the core I left at AutoZone. Doh! this sensor can be removed before removing the booster from the firewall, and will give you additional room to work. However, MAKE SURE you have a clip placed on the replacement booster before you install it. its much easier to move it when both boosters are in your hands, not in the car. The sensor can then be placed in the unit after nearly everything is buttoned up.

All that said, if I was going to do this job again, I would remove the master cylinder, and see if that allows enough room to get the booster out without pulling the air box, fuse box, etc.... It would not be that big of a job to then bleed the brake system- actually it would be a complete flush, which my shop will do for $40- and since it is a good idea to flush the brake system every couple of years anyway- might be a better route to go. I might even go so far as to replace the master cylinder with a new unit, as the warranty on the booster will void if any brake fluid is found on it!

Furthermore, after replacing the booster, I note the under dash hiss is gone- other than the normal one when pressing the pedal. Also, the brake boost is better, easier stops. However, the vacuum motor still runs as much as it ever did. Since there are new O rings on the master cylinder to booster mount, and on the Brake Booster Diaphragm Position Sensor- and the grommet for the vacuum line was new on the replacement booster, I figure it has to be somewhere down the line-
Vacuum pump
Brake Booster Vacuum Switch
Check valve(s)?
Hoses?

 

Thanks for the information but the most common reason why a brake booster fails is because the master cylinder is leaking. Your mechanic should inspect the master cylinder to ensure there are no leaks.

 

Great information folks... thanks for that!
Newbie question.
Just bought an 01 xc 70 for dirt cheap because abs service required light was on. I've read about the guy who will rebuild them for less than $200 so I figured it was a great deal. Went to pick car up and every warning light was on including "brake failure. Service urgent". Dealer replaced entire brake system from master cylinder, all lines, new pads, rotors, and remanned calipers. All at his expense which was more than I paid for car.
Question is... I still have the traction control warning light on, but I have no STC OR DSTC button on center console (or anywhere else that I can find). Is it possible my car has neither? If so, how do I figure out what tc warning light means? If not, how can I tell which it has without going to booster? I have no tc service warnings... just abs service and bulb position sensor.
Any thoughts, ideas, suggestions, hypotheses welcome. Thanks again for the depth of enthusiast assistance.

 

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More actions Plus my local engineer charged $300 nz to change it made a hell of a difference. If the booster is leaking round the seal on the peddle input shaft then the Bellophram is stuffed and a new booster is required don't play around with it just cough up and have a new one fitted EBAY has plenty just make sure it is the correct one for your model. DSTC is considerably more expensive This was on a S80 T6 with DSTC.

 

Tech,
Thanks for this writeup. I found it very helpful. A couple points I learned on an S80 T6 replacing the brake booster.
1. You have to remove the air intake that goes to the back of the engine. Just a clamp on each end.
2. The sensor is held in by a ring. You can pry it out with a screw driver to safely remove the sensor from the old brake booster.
3. Make sure you carry over the rubber o-ring for the sensor to the new brake booster. It won't seal without it. (Guess how I know?)